31. The room is in a terrible mess; it _______ cleaned.
| A．can’t have been | B．shouldn’t have been |
| C．mustn’t have been | D．wouldn’t have been |
He thought that painting copied by a modern artist was ______ great value and bought it ____ over a thousand dollars.
| A．at; for | B．of; for | C．of; at | D．for; by |
Let him who tied the bell onto the tiger take it off -- _____ started the trouble should end it.
| A．whomever | B．who | C．whoever | D．anyone |
Social networking is an important factor _______ business success.
| A．devoting to | B．appealing to | C．attaching to | D．leading to |
Duri
ng the expedition in the mountains we passed through a place where in a little while we all lost out ______ of direction.
| A．sense | B．feeling | C．idea | D．ability |
He is free now, so he ______ go with us, but he hasn’t decided yet.
| A．shall | B．must | C．may | D．will |